Some engines utilise a high-density hydrocarbon propellant fuel that typically comprises exo-tetrahydrodicyclopentadiene. The engines that use such fuel are typically of the miniature gas turbine or turbojet type with approximately 150 lb-f thrust or less. They generally power airborne vehicles of the single use or expendable type, such as reconnaissance drones, cruise missiles, decoys and other weaponry, including air-launched and ground-launched weapon systems. Such engines provide greatly extended range compared to conventional solid fuel rocket engines in such vehicles.
Military Standard MIL-P-87107 describes such a high-density hydrocarbon fuel for gas turbine and turbojet engines. A common name known in the industry and military fuel depots for this fuel is JP-10. JP-10 is becoming predominant in the military for missile and aircraft applications due to its favourable properties, which include high density and chemical stability, thereby providing extended vehicle flight range as well as long-term storage.
It is advantageous to use the fuel as a lubricant for the engine in such expendable vehicles because it eliminates the cost and weight of an independent lubrication supply system. However, JP-10 as generally manufactured is a poor lubricant for bearings in the miniature gas turbine engines that are used in such expendable vehicles. A fuel additive known as tricresyl phosphate (TCP) added to JP-10 may make JP-10 suitable as a lubricant for miniature gas turbine engine bearings.
It is convenient for the manufacturer of expendable vehicles to add TCP to JP-10 when expendable vehicles when the manufacturer fuels the vehicles at the factory. However, since the military and prime contract customers use JP-10 fuel for numerous applications, it is logistically more practical for military and prime contractor end users to use a single storage tank of pure JP-10. In addition, end users are reluctant to mix TCP with JP-10 for unique applications.